The operation of drilling by machining includes producing a hole using a tool such as a drill bit with an axis of rotation, the tool being driven by cutting movement which corresponds to rotation of the tool around itself according to its axis of rotation, combined with movement of advance which corresponds to movement of translation of the tool according to its axis of rotation.
The drilling operation can be carried out using a machine tool or an articulated arm of a robot. In these cases, the movements of cutting and advance are imposed by actuators such as motors for example, and are perfectly controlled.
In the aeronautical field, the operation of drilling into a part can be carried out by a portable drill.
In a known manner, a portable drill comprises a body which is intended to be held by a user, with a head equipped with a chuck in which a tool is inserted. The body comprises a motor to which the chuck is connected, and which imposes cutting movement on the chuck.
In the case of a portable drill, only the cutting movement is imposed by the drill. The movement of advance is imposed by the user who is holding the drill, and applies a force on the drill in the direction of the part to be drilled.
However, for certain applications such as drilling into composite materials, it is essential to control the movement of advance in order to avoid phenomena of delamination or scaling if the movement of advance is too rapid, or burning phenomena if the movement of advance is too slow.
Control of the movement of advance by the user requires great dexterity. This control is all the more difficult as the user is exerting a significant force.
In order to better control the movement of advance, a device for control of advance is known which is secured on the portable drill.
It comprises a jack with a body which is rendered integral with the manual drilling apparatus, and a piston which slides in the body and supports a rod, an end of which is situated on the exterior of the body.
The piston delimits together with the body two chambers, each of them being filled with a fluid and communicating with the exterior via a fluid network. The device for control of advance also comprises a control the filling and/or emptying of the chambers in order to control the movement of translation of the rod, which is mobile between an extended position and a retracted position.
According to this device of the prior art, before the drilling, the rod is in the extended position, and its end is supported against the part to be drilled. During the drilling, the force exerted by the user on the drill in the direction of the part causes by reaction a force of the part on the rod of the jack, which is then translated into the retracted position. This movement of translation gives rise to filling of a first chamber and emptying of a second chamber. According to the prior art, it is then possible to control the advance of the tool by braking the movement of the rod, by controlling the filling and/or the emptying of at least one of the chambers.
This device for control of advance is not fully satisfactory because of its dimensions. Thus, the part to be drilled must have a large flat surface area around the hole to be produced, in order for the rod to be able to be supported against the part to be drilled, and this is not always the case. In addition, the presence of a rod which is mobile according to a direction parallel to, and spaced from, the axis of the drill bit results in large dimensions around the drill bit, which can be problematic when drilling a hole in an area which is not very accessible.